Proportional interpolator



Feb. 2, 1954 c. J. ACKERMANN PROPORTIONAL INTERPOLATOR Filed June 19, 1951 NVENTR.

AT1-ORN r-:Ys

y .navll Patented Feb. 2, 1954 UNITED STATES PATENT OFFICE (Granted under Title 35, U. S. Code (1952),

sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, Without payment to me of any royalty thereon.

The present invention relates to improvements in geometrical instruments and in particular to an instrument for the subdivision of any distance into any number of equal parts or parts of any desired ratio by the application of geometrical principles.

Various instruments have heretofore been constructed to permit the rapid application of principles of geen etry to the solution of specific types of problems, the said instruments being substituted for the laborious and time-consuming methods involving the standard drafting instruments, but no instrument of this type is known to have been devised for the rapid geometrical solution of the problem of the subdivision of any distance into 'any number of equal parts or parts of any desired ratio.

Principles of geometry heretofore normally have been applied to the subdivision of any given distance into any given number of equal parts,

or parts in any desired ratio, using a straight Y edge and a draitsmans triangle or a compass by constructing a line of any length already divided into the Adesired number of parts at an angle to one end of the line ultimately to be divided so as to form a second leg of a triangle therewith, drawing the base line of the triangle, and projecting lines through the known divisions on the constructed line parallel to the base line and through the line to be divided. This method is slow and laborious and produces results in which human error is magniiied.

An important object of this invention is to provide a single instrument that may be used to divide any given distance into any given number of equal parts while the instrument remains at one location during the process so as to minimize human error.

Another important object of this invention is to provide a single instrument for the application of the geometrical principle that if three or more parallel lines out 01T equal segments on one transversal, they out ofi equal segments on every transversal, to the physical solution of geometrical problems.

Another important object of this invention is to provide a single instrument that may be used to divide any given distance into any number of parte which among themselves have any desired ratio.

Still another important object of this invenbodiment of the improvements comprising the invention.

In the drawings,

Fig. 1 is a plan view of an exemplary embodiment of the invention in a position of use and with successive parallel lines that may be drawn by the one straight edge indicated by dotted lines;

Fig. 2 is a section taken on line )SI-II of Fig. l but with the straight edges in folded position parallel to the base member;

Fig. 3 is a perspective View of the base member of the device with all other elements removed; and

Fig. 4 is a detailed section taken on line lvl-IV of Fig. 1.

In the drawings, wherein for the purpose of illustration, there is shown a preferred embodiment of the invention, the proportional interpolator is indicated generally by reference numoral I and includes base member 2, scale 3, straight edged rules or ruler arms d Iand 5 and slide 6 as principal components. Base member t is an elongated block having straight longitudinal edges l and il suiiiciently Wide to have a beveled surface 9, slot lil and channel il and sufficiently thick to have both channel l l and a cut-away portion defined by walls i2, i3, Ed and i5. The base member is beveled adjacent the longitudinal edge 1 to form a beveled surface 9 in which is cut a track groove lo parallel to edge l. Groove it is out with diverging Walls so that the base of the groove is Wider than the mouth and is coextensive in length with the base member. This track groove i6 receives a sliding scale as will be explained in detail below. Longitudinal channel l i is cut into the top surface of the base member parallel to edge l and terminates short of the ends of the base member. Slot it, also parallel to edge l, extends through the base member from the bottom of the channel ll, but is shorter and more narrow than channel l i so as to dei-lne shoulders I1 and I8 and platforms i9 and 29 of 'Scale 3 is an elongated ruler having two4r straight parallel edges 23 and 24 anda tongue 25 projecting from one side midwayv between the edges 23 and 2d which is keyed to slidably and reversibly fit the track groove l. The' scale isr preferably constructed with a beveled top surface to present very narrow straight edges at 23 and 25, and is so proportioned that the straight edge presented is substantially superimposed on longitudinal edge l of base member 2. The scale 3 is calibrated along each edge 23 and 24) in different units, for example inches, `along one edge, and millimeters along the other, or two different or arbitrary systems, the only limitation necessary being that all units along one edge be identical.

Slide s is a rectangular block of width to be slidably received in channel l l, Without wobbling movement when operated, and has a reduced portion or boss 2t slidably received in slot l@ which also aids in preventing undesired wobble. The reduced portion 2li when fitted in slot IQ extends just slightly beyond surface l5 as indicated by Z'l into the cut-away space at the bottom of the base member. Slide e is bored at 28 to receive bolt 29 which is fitted with washer 39 and wing nut 3i. Straight-edged rule t is a long narrow strip approximately the'length ofj slot lil and, as illustrated, has beveled edges presenting fine line edges and has a hole 32. Rule or ruler arm is attached parallel to the wall l5 of the base member 2 by means of bolt 2S which forms a pivot means for the rule and which, in cooperation with the rule, serves to retain the slide 6 in the slot l@ and channel ll. The extension of reduced portion 2t of the slide beyond wall l5 allows the slide and rule 5 to slide longitudinally of the base member without excessive friction with wall l although wing nut 3l is tightened to prevent angular displacement of the slide and rule Straight-edged rule or ruler arm d is identical to rule 5 except that rule d has a boss 33 on one side about hole 313 which serves to space rule li from wall it suiciently to pass rule 5 when the rules are in overlapping position. Straightedged rule i is pivoted to the base member by bolt 35 which is also provided with a washer 36 and Wing nut el and which is placed through either hole 2l or 22 serving therein as a pivot means for the rule. Therefore, straight-edged rules Ll and 5 may be pivoted about their respective pivots from an overlapping position parallel to the base member to positions at any angle to the base member and in themselves intersecting or not.

The operation of the device is best explained in connection with the solution of a given problem. In Fig. i points A and B are two pointsL the distance between which is to be divided, for purposes of illustration, into 10 equal parts. Although either side of the scale 3 may be used, it is most convenient to use the side on whichv 1 0 units ormultiples thereof most nearly approximate the distance from A to B. The selected calibrations are Placed adjacent to edge, l Qi the.

4 base member, scale 3 may be reversed if necessary. With bolt 35 in secured position in either hole 2l or 22, wing nut 3l is loosened and rule A placed at any convenient angle to edge 1 and wing nut 31 tightened to maintain rule ll in that position. The instrument is then placed on the worlg surfacewith the intersection between the edge of scale 3 and the edge ofrule e on the side toward rule 5 being placed at point A and the same edge of rule passing through point B as illustrated in Fig. 1. Scale 3 is then slipped longitudinally to present a calibration mark at point A and with at least the desired ten units (or selected multiples thereof) extending toward rule Ei. Wing nut 3| is then loosened and rule 5 and slide 6 are then moved so as to place the edge of rule 5 nearest rule i in a position indicating the line between point B and that point that is the end of ten units (or multiples thereof) from point A along scale 3 and is herein identied by C. Wing n lt 3l is then tightened to maintain the angular relationship between rule 5 and slide G. G is moved, rule 5 will define only lines parallel to the line B--C.

Because of the principle of plane geometry to the effect that if three or more parallel lines cut oif equal segments on one transversal, they cut off equal segments on every transversal, then nine lines (indicated by dotted lines in Fig. 1) parallel to the line B-C at the calibrations between A and C cut the distance A-B into `the desired ten equal parts.

The device may also be used to divide any given distance into any number of parts having any desired ratio other than equal or 111:1, in any order such as, for example,l four parts in the ratio of 2:7:1:3. This may be readily accomplished by setting point C (see Fig. 1) from point A the number of units that is the total of the figures representing the ratio (in this illustration 1 3) and counting off the units according to the ratio to establish the lines parallel to line B--C.

It is to be understood that the form of the invention herein shown and described is a preferred embodiment of the same and that various changes in size, shape and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the following claims.

Having thus described my invention, what I claim as new and wish to secure by Letters Patent is;

1. A geometrical instrument for the division of a given distance into any number of equal or proportional parts comprising an elongated base member having a straight longitudinal edge, said base member being tapered on one :tace toward said edge, and being recessed on the face opposite the taper; said base member being formed with an elongated slot parallel to and spaced from said straight longitudinal edge and with a hole through the base member at one end of said slot, said hole being in line with and spaced Slightly from the end of said slot; a iirst removable pivot means in said hole; a drst straight-edged rule, removably pivoted adjacent one end thereof to the base member by said first pivot means and lying ina plane parallel to out spaced from the plane of said straight longitudinal edge andthe interior surface ci the recesscd portieri Qf the, bese member; means for immobilizing said first rule with respect to said pivot means; @enacted Slide removably It is now evident that as slidesecured in said slot for movement longitudinally thereof; a second pivot means on the slide; a second straight-edged rule in a plane parallel and contiguous to the planes of the said irst rule and said base and being removably pivoted at one end thereof to the slide by said second pivot means whereby the tWo said rules may be pivoted from positions within the recessed portion of the base member to positions or" inter-- section in space beyond said straight longitudinal edge of the base member With said rules, said point of intersection and said straight longitudinal edge substantially in a common plane; means for immobilizing said second rule with respect to said second pivot means; said base member being formed with an elongated dove tailed track groove on the tapered portion of the base parallel to both the said straight longitudinal edge and the said slot and intermediate thereof, and extending the entire length or" the base; and an elongated scale being tapered to a straight edge having calibrations and being provided with a projecting dovetailed tenori, each extending the length of the scale, mounted on the tapered portion of said base with said tenon engaged in said track groove and with said straight edge of the scale being immediately superimposed on said longitudinal straight edge of the base whereby the rst straight-edged rule may be set at an angle to the base and placed along the distance to be divided with one end of the distance at the intersection of the rule and the straight longitudinal edge, the scale moved so that one end also corresponds -to said one end of the distance, the second straight-edged rule set to indicate the line between the other end divided and a calibration is divisible by the number of equal parts into which the given distance is to be divided or the common denominator of proof the distance to be value on the scale that portional parts, and the slide moved to propel the second straight-edged rule in a plane contiguous to said irst rule through parallel positions Which will divide the given distance into the desired portions.

2. The structure of claim 1 wherein said recessed portion of said base member is dened by a margin of said opposite face of the base member extending along the longitudinal edge opposite from said straight longitudinal edge of the base member and along both ends of the base member and wherein the depth of said recessed portion is at least equal to the combined thicknesses of said irst and second straightedged rules and wherein said rst straight-edged rule is oifset from the interior surface of said recessed portion at said rst pivot means by the thickness of said second straight-edged rule.

CASPER J. ACKERMANN.

References Cited in the le 0f this patent UNITED STATES PATENTS 

